Gaskets

ABSTRACT

Rubber gaskets internally reinforced with flexible relatively incompressible, preferably fibrous material and externally coated with rubbery material such as coagulated neoprene latex and preferably having at least one concave surface are described. The preferred gaskets are designed to receive a structure to be sealed within the concave surface so that the structure contacts the concave surface in at least two sealing lines. The gaskets are further characterized by having relatively thin rubbery coatings on certain surfaces and relatively thicker coatings on other surfaces in order to provide improved sealing integrity; the thickness of said relatively thin and thick coatings being specified. Methods of making the gaskets are also described.

United States Patent 1 1 Kwok 1 1 Apr. 24; 1973 1 1 GASKETS FOREIGNPATENTS OR APPLICATIONS 7 Inventor; Michae] Kwok, 5 Cedar Lane,1,252,163 12/1960 France ..277/228 Princeton, NJ. 08540 PrimaryExaminerMeyer Perlin [22] Filed: Jan. 7,1971

Appl. No.: 104,575

Related U.S. Application Data Assistant Examiner-Ronald C. CaposselaAttorney-Howson and Howson [57] ABSTRACT Rubber gaskets internallyreinforced with flexible relatively incompressible, preferably fibrousmaterial and externally coated with rubbery material such as coagulatedneoprene latex and preferably having at least one concave surface aredescribed. The preferred gaskets are designed to receive a structure tobe sealed within the concave surface so that the structure contacts theconcave surface in at least two sealing linesv The gaskets are furthercharacterized by having relatively thin rubbery coatings on certainsurfaces and relatively thicker coatings on other surfaces in order toprovide improved sealing integrity; the thickness of said relativelythin and thick coatings being specified. Methods of making the gasketsare also described.

3 Claims, 10 Drawing Figures Patented April 24, 1973 3,729,205

- INVENTORI MICHAEL KWOK BY W-JW ATTVS.

GASKETS This application is a continuation-in-part of my earlier USpatent application, Ser. Number 760,1 l8, filed Sept. 9, 1968 nowabandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to novel gaskets and is especially applicable to gaskets for usein sealing automotive valve covers.

2. Description of the Prior Art Of the many types of gaskets available,several have been used previously for sealing automotive valve covers.The gaskets which have been most commonly used for this purpose arecomposed of cork or molded rubber and are integrally formed of a singlematerial. The composition cork gaskets are highly compressible, but havegood resiliency and recovery properties and resist the corrosive effectsof hydrocarbon products found in the automotive environment. Suchgaskets perform satisfactorily for a short period of time, buteventually fail as valve cover gaskets due to normal repeated heatingand cooling, which tends to set the cork. These gaskets also fail due toopening of the seal caused by engine vibration. Therefore, prolongedpositive sealing of valve covers has not been achieved with a corkgasket.

On the other hand, available oil-resistant rubber gaskets, while havinggood aging,heat and oil resistance, even under sever operatingconditions, lack resistance to cold flow under compression and tend tocreep, thus damaging the seal.

A third type of gasket combining the properties of the cork and rubbergaskets is also known in the art. Typically such gaskets consist of aninternal fibrous or cork structure with a rubber coating formed over theinternal structure. Such gaskets combine the desirable properties ofboth cork and rubber gaskets, since the inner structure is relativelystiff and resistant to deformation or cold flow," while the outersection is com formable to the flanges or other mating surfaces whichthey seal. These gaskets are also resistant to heat and oil.

However, presently known gaskets having an internal fibrous structureand an external or outer rubber coating are formed by a dip-coatingmethod, or by die cutting gaskets from a rubber-coated fibrous sheetmaterial. Neither of these methods is suitable for making gaskets havingdesirable thick coatings of rubber on the upper and lower surfaces. Inthe dip-coating method, uniformity of coating thickness cannot beaccurately controlled. Moreover when gaskets are dipped to obtainrelatively thick coatings on the upper and lower surfaces, thickcoatings are necessarily obtained on the edges of the gaskets as well.Such thick edge coatings render the gaskets unsuitable for certainapplications.

In the die-cutting method, in which the gaskets are cut fromrubber-coated fibrous sheet material, the edges of the fibrous insertare exposed, thus enabling oil to penetrate into the gasket and causingthe rubber coatings to peel from the fibrous body member. This method offorming such gaskets is also uneconomical due to the high percentage ofscrap formed in cutting gaskets from sheet material. The cost of formingheavy coatings on the upper and lower surfaces of a sheet materialaggravates the uneconomic scrap problem.

Therefore, the optimum automotive valve cover gasket would be onecomprising a fibrous insert provided with a relatively thin coating ofrubber along its edges and a relatively thick coating on its upper andlower surfaces. With such a design, the surfaces for contacting themating flanges to be sealed would be provided with a maximum amount ofresilient material, while the rubber coatings on the gasket edges wouldbe of a thickness just sufficient to prevent the oil from penetratinginto the gasket and maintain the integrity of the assembly by obviatingthe tendency of the coating to peel off the fibrous body member. Sincethe fibrous insert would improve the creep resistance of the gasket,extremely low durometer rubber compounds could be incorporated into thegasket without fear of the gasket being extruded in use. Whileautomotive valve cover gaskets, in particular, have been generallyplanar in form in the past, it would, of course, be desirable to developother configurations providing improved sealing integrity.

SUMMARY OF THE INVENTION It is, therefore, an object of the presentinvention to provide novel gaskets comprising an inner fibrous sectionand an outer soft rubber or rubber-like covering which is relativelythick on the sealing surfaces such as the upper and lower surfacesthereof, and any sealing edge or edges, and relatively thin on theremaining edges of the gasket. The preferred novel gaskets of theinvention also have at least one concave surface to provide two lines ofsealing contact with a surface to be sealed, such as the flange of anautomotive valve cover. Such linear seal lines provide satisfactorysealing integrity at a lower compression than is possible with a sealingsurface of greater width. The relatively thin edge coatings on thoseedges of the gasket not requiring a thick coating for sealing integrityare employed to complete the envelope of rubbery coating around thefibrous insert. In this way, the unity of the gasket is ensured whilestill permitting the fibrous insert to extend substantially to the edgeof the gasket, thus providing increased resistance to cold flow orcreeping of the gasket under compression.

The gaskets of the present invention may be produced by suspending anessentially imperforate fibrous insert structure smaller than, butconfigured in accordance with the ultimate gasket structure, in a moldsuch that the lower surface of the fibrous insert member issubstantially the same distance from the bottom of the mold as the topsurface thereof is from the top of the mold. An auto-setting compound,for example, of neoprene latex containing a coagulant such as sodiumsilico-fluoride, is then poured into the mold and allowed to set.Finally, the composite gasket is removed from the mold. Consequently bychoosing an appropriately sized fibrous insert member and properlypositioning it in the mold the latex surface of the gasket can beprovided with any desired thickness at any point. For example, bychoosing a fibrous insert almost as wide as the mold, only a very smallarea remains between the edge of the fibrous material and the side wallof the mold interior and a gasket is obtained having a thin edge coatingof neoprene.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of thegasket.

FIGS. 2a-d are cross sections of the gasket.

FIGS. 3a-d are cross sections of the gasket with sealing surfaces.

FIGS. 4a-b are cross sections of the gasket.

DESCRIPTION OF THE PREFERRED EMBODIMENT As a typical example of thegaskets of the invention, an automotive valve cover gasket isillustrated in top plan view in FIG. 1. While the illustrated gasket 10has a typical configuration, any other configuration either entirelyclosed, or having a cut-out portion 12 as shown, may be employed. Asseen in FIG. 2a, for example, the gaskets include a fibrous or otherflexible but relatively incompressible insert 14 covered with a rubberycoating 16, suitably of neoprene latex or other rubber-like material.One preferred embodiment of the invention shown in FIG. 2a has a concaveupper surface 18 and a concave lower surface 20. It should be noticed,also that the rubbery coating 16 is relatively thick above and below thefibrous insert 14 in the area of the concave surfaces 18 and 20, but isrelatively thin at the edges of the gasket 22 and 24.

Other embodiments of the invention are shown in cross section in FIGS.2b, 2c and 2a. These embodiments differ from that of FIGS. 1 and 2a onlyin that one or more surfaces 26 of the gasket are planar rather thanconcave.

While gaskets of the invention having two planar sealing surfaces, asshown in FIG. 2d, represent a definite improvement over the prior art inthat they have the relatively thick rubbery coatings on the sealingsurfaces and relatively thin coatings on the edges characterizing suchgaskets, they are less preferred than gaskets such as those shown inFIGS. 2b and 2c and particularly the gaskets of FIG. 2a, which haveconcave sealing surfaces.

As best seen in FIG. 3, a member to be sealed, such as a generallyrectangular edge or flange of an automotive valve cover 28 is preferablyintroduced into a concave surface of a gasket of the invention and urgedthereagainst so that the edges of the flange 28 contact the concavesurface of the gasket in two or more linear seals. In this way excellentsealing contact is achieved along the linear contact areas with aminimum of compressive force. As seen in FIG. 3a the fibrous insert 14may be co-extensive with or even in excess of the width of the flange 28with the coated edges of the gasket protruding exteriorly of the flange.As shown in FIG. 3a, the two flanges 28 and gasket 10 are shown in theirassembled relation but in an exploded" or less than normally compressedcondition for purposes ofillustra tion. Under normal sealing conditionsthe flanges 28 would be pressed more tightly against the gasket 10 thuscompressing the resilient concave surfaces 18 and and broadening theareas of sealing contact along the original seal lines indicated atpoints 30 and 32. Compression of the outwardly flared portions of theconcave surfaces 18 and 20 tends to force portionsof the thus distortedor stressed rubbery coating inwardly thus thickening the coating in thecentral portion of the concave surfaces and causing it to bulge away butnot separate from the central insert toward the adjacent flange 28.

As seen in FIG. 3b the gaskets of the invention may also have one planarsealing surface 26 in contact with a flange 28 and another concavesurface in contact with another flange 28. Similarly, the gasket of FIG.2d having two planar surfaces 26 would form a flat seal on each surfaceas shown with respect to the upper surface of the gasket in FIG. 3b.

The gaskets illustrated in FIGS. 2, 3 and 4 have relatively thick upperand lower rubbery coatings over the insert 14 on surfaces 18, 20 and 26,and relatively thin rubbery coatings on the edges 22 and 24 of thegaskets. The invention also includes gaskets having a relatively thickrubbery coating 36 on one or more edges of the gasket, as shown in FIGS.4b and 5. While the thicker coating has been shown on the inner edge ofthe gasket in FIGS. 4b and 5 it could as well be on the outer edge ofthe gasket if necessary or desirable. Such relatively thick edgecoatings are desirably employed adjacent fluid reservoirs to be sealedor other sources of liquid or gaseous pressure as, for example, on theinner edge of an automotive valve cover gasket in contact withhydrocarbon oil.

As seen in FIG. 5 of the drawings, the novel configuration of thepreferred gaskets of the invention employing concave upper and lowersurfaces, for example,

presents a generally wedge-shaped gasket configura- 1 tion to the sourceof fluid pressure to be sealed. Therefore, fluid pressure directedtoward such a wedgeshaped gasket configuration, as seen in FIG. 5, tendsto force the wedge into the space between the flanges 28 to be sealed.This forcing of the wedge into the aperture to be sealed, of course,increases the effectiveness and integrity of the seal. This is incontrast to the situation with a non-compressible planar gasket wheresuch edgewise pressure would tend to force the planar gasket through andpossibly out of the space to be sealed between the flanges.

Inasmuch as even the planar gaskets of the present invention have acompressible rubbery coating over the relatively stiff and relativelynon-compressible fibrous insert, in all cases where the flanges 28contact the surfaces of the gasket from either side under normalcompression, the flanges indent the rubbery coatings thus causing arelatively elevated portion of the rubbery coating to form adjacent thesealed edges of the flanges. This relatively elevated portion actssimilarly to the wedge shaped configuration of the concave-surfacedgaskets as described above, although to a lesser degree. It will beobvious that this is also the case with a gasket of the invention havingone planar surface and one concave surface as shown in FIG. 3b.

It is especially preferred that the edge of the gasket adjacent anysource of fluid pressure, as edge 36 in FIG. 5, have a relatively thickcoating of rubbery material in order to increase the effectiveness -ofthe wedge configuration and the integrity of the seal.

MANUFACTURE OF THE GASKETS Although any suitable method may be employedto manufacture the gaskets of the invention, in the preferred procedurean essentially imperforate fibrous insert saturated with latex is cut orformed to the desired size andsuspended in a gasket mold by means ofpins depending from a frame which may take any suitable form, such asthat of a strip of spring steel on edge having a contour similar tothatof the gasket and mold. Next, a compound of neoprene latex isprepared with a coagulant additive such as sodium silicofluoride.Immediately after adding the coagulant, the autosetting compound ofneoprene latex containiing the coagulant is poured into the mold to thedesired height. The latex is then allowed to set up, which normallytakes about three to 5 minutes. In practice, it has been found that thefinished gasket can be removed from the mold after about ten minuteshave elapsed from the time the latex compound was initially poured intothe mold.

With respect to the first step, the material for the fibrous insert canbe chosen from any group of materials that will exhibit inherently goodload bearing and creep resistant characteristics. Such materials includecomposition cork, sheet metal, wood, plastics and the like, but moretypical materials would be cotton linter board, mercerized wood pulp ordissolving wood pulp, saturated with neoprene, buna N, or acrylicrubber. The versatility of the present invention is seen in this firststep wherein the fibrous insert can be cut to any desired size tothereby dictate the thickness of the coating which will ultimately formaround each surface of the fibrous insert. This follows naturally sincethe structure of the mold and the insert cooperate to limit the usablearea into which the latex compound can be poured. To produce a gasket ofthe present invention with relatively thick upper and lower surfacecoatings but relatively thin edge coatings, the fibrous insert should becut or formed to a thickness which will allow a suitably thick upper andlower coating of latex. Conversely, the insert should be formed to awidth which will afford only a very small area between the edges of thefibrous insert and the respective edge walls of the mold to limit thethickness of the coating which can be formed along the edges of thegasket. Of course, where a relatively thick edge is desired more spaceisleft between the edge of the insert and the wall of the mold on theedge or edges where the greater thickness is desired.

The next step relates to suspending the fibrous insert from the pinsfixed to and depending from the frame.

The mold and the pins depending from the frame are arranged to providean assembly which will cooperate to allow for the mounting of thefibrous insert at any desired elevation within the mold. Accordingly, itcan be seen that the mounting of the fibrous insert on the pinsdetermines the distance between the insert and the base or bottom of themold. Consequently, an additional element of versatility which inheresin the present method for producing gaskets can be seen in the fact thatthe insert can be mounted at any elevation on the pins. However,practice has taught that locating the fibrous insert substantiallycentrally within the mold provides the optimum results since with thisarrangement the upper and lower neoprene latex coatings will be formedwith equal thicknesses.

The next step requires the preparation of the desired auto-settingneoprene latex compound for the gasket surface. A variety of neoprene orother rubber compounds can be used and accordingly the application forwhich the gasket is desired will normally dictate the compound to beused. However, neoprene latex compounds such as those set forth belowhave been found to be most suitable for use in making gaskets forautomotive valve cover applications.

Dry

Example 1. Single latex Parts Percent Neoprene Latex 842A*"* I00 85.5Zinc Oxide Dispersion l5 12.8 AgeRite White Dispersion" 2 1.7 Totals l17 100.0

Example 2. Latex blend Neoprene Latex 570**** I00 78.7 Hycar Latex 1551*10 7.9 Zinc Oxide Dispersion* l5 1 1.8 AgeRite White Dispersion 2 L6Totals I27 l00.0

*Curing agent for neoprene latex "An antioxidant for oxidationprotection "Butadiene/acrylonitrile type latex consisting of copolymersof bu tadiene and acrylonitrile, OR type for oil resistance, availablefrom the B.F. Goodrich Co.

""Neoprene Latex 842 A and 571 are commercially available long chainsynthetic rubbers made by polymerization of chloroprene(monochloro-butadiene H C=CHCCI=CH The preparation of the compoundshould include the addition of a coagulant such as a dispersion ofsodium or potassium silicofluoride, mixtures of the two, or otherequivalent coagulants, immediately before pouring the latex into themold. The addition of coagulant, of course, provides the means by whichthe neoprene latex compound is coagulated into its final set form, sincethese materials cause a drop in pH in the latex system which acceleratessetting of the rubber particles in the latex. It should be noted thatsome shrinkage occurs due to evaporation of the water in the latex as itsets up.

The next step required is pouring the compound of neoprene latex withadditive into the mold to either a level indicated on the mold or to thetop of the mold, if the mold is so sized. The auto-setting compoundcontaining a coagulant formed as described above will set up inapproximately 3 to 5 minutes, and the finished gasket can be removedfrom the mold about 10 minutes after the latex compound is first pouredinto it.

A gasket formed in this way in an open topped mold having a flat bottom,will have the cross section shown in FIG. 2a. The latex shrinkssubstantially on drying and due to this fact and the presence of thedimensionally stable insert suspended in the mold, the gasket will haveconcave upper and lower surfaces 18 and 20, respectively. The shrinkageof the latex also causes a slight beveling of the edges of the finishedgasket as shown at points 38 in the cross-sectional view of FIG. 2a.

In order to achieve a gasket having a cross-section such as that shownin FIG. 2b, it is necessary to slightly overfill an open mold so that aconvex meniscus of the latex compound is formed above the insert andupper edges of the mold. Shrinkage on drying causes the convex meniscusto recede to form a planar upper surface 26 on the finished gasket.

In order to obtain a gasket having a planar lower surface 26 as shown inFIG. 2c, a mold having a concave depression in its bottom may be used toaccommodate excess latex compound, which on drying shrinks to providethe desired planar surface.

The gaskets of FIG. 2d may be obtained similarly by using an open moldhaving a concave bottom and overfilling it to provide a convex meniscusabove the upper edge of the mold. On drying, shrinkage of the upper andlower convex latex surfaces around the fibrous insert, provides a gaskethaving planar upper and lower surfaces. These gaskets also have bevelededges due to the shrinkage of the latex cover.

The overall dimensions of the gaskets are, of course, determined by theexisting specifications for the particular application or use. Forexample, 0.5-inch gasket may be designed to have an overall width ofthat dimension. The fibrous insert normallywould then be selected tohave a width slightly less than 0.5 inch in the range from about 0.312to 0.468 inch; the thickness of the finished coating of latex on thegasket being from 0.016 to 0.094 inch. It will be seen that when such agasket 0.5 inch wide, consisting of an insert 0.468 inch wide coatedwith latex and having latex edges 0.016

inch wide, is placed between a pair of flanges 0.5 inch wide, that theinsert extends nearly the full width of the flanges, leaving on the 0.16inch width of the latex edge on each side unsupported by the insert. Itwill be seen, therefore, that such a gasket provides assurance againstcold flow or creeping due to the fact that the non-compressible fibrousinsert extends nearly the full width of the flanges being sealed.

Preferably a somewhat oversize gasket is employed as shown in FIG. 3. Inthis case the width of the gasket insert is equal to or even in excessof the width of the flanges to be sealed and the latex edges, of course,protrude from either side of the flanges as shown. Here again, thegaskets prevent cold flow or creeping, since the entire width of theflanges is supported by the internal fibrous insert. Greater sealingintegrity is provided by the gaskets of this embodiment due to theprotrud-' ing wedge shaped latex edges of the gasket.

The thickness of the new gaskets and the thicknesses of the relativelythick and thin latex coatings is important to the proper functioning ofthe gaskets for use in sealing automotive valve covers, for example.These dimensions are set forth in Table I below.

TABLE I GASKET DIMENSIONS Thickness in Inches Approximate Range MaximumMinimum Preferred It will be seen from Table I above, that the finished,dry latex coatings on the new gaskets may vary from a minimum thicknessof about 0.016 inch to a maximum thickness of about 0.094 inch. Thepreferred thickness of the latex coatings on the upper and lowersurfaces of the gaskets is about 0.047 inch. The preferred thickness ofthe latex edges is about 0.031 inches. The dimensionally stable fibrousor other inserts may vary from about 0.031 to 0.094 inch in thicknessand is preferably about 0.062 inch. Therefore, the finished gaskets havean overall thickness of about 0.062 to about 0.25 inch and arepreferably about 0.156 inch in thickness.

In view of the above, the terms relatively thick and relatively thinused herein have the following meanings: As all dimensions herein aremeasured at the point of minimum thickness in the area referred to, i.e.in a concave surface the thickness is measured at the center of thesurface rather than at the thicker edges thereof. As to the upper andlower latex surface coatings on either side of the fibrous insert, sincethe preferred thickness is 0.047 inch, any coating of that thicknessor'thicker up to the maximum of about 0.094 inch is a relatively thickcoating, and any substantially thinner coating down to the minimum ofabout 0.016 inch is a relatively thin coating. Similarly, since thepreferred thickness of the latex edge coatings is about 0.031 inch anycoating of that thickness or thicker up to the maximum of about 0.094inch is considered a relatively thick edge coating, and anysubstantially thinner coating down to the minimum of about 0.016 inch isconsidered a relatively thin edge coating.

It will be apparent from the above that the novel, internally reinforcedrubber gaskets of the invention, whether of the double planar surfacetype of FIG. 2d or one of the preferred embodiments having at least oneconcave surface, provide creep resistant sealing integrity forautomotive valve covers or use in a wide variety of other applications.It will also be apparent that the preferred gaskets with the concavesurfaces provide for sealing at relatively low initial compression thusquickly and efficiently compensating for any imperfections of thesurfaces of the flanges being sealed. Moreover, as shown in FIG. 3, whenthe flange to be sealed is inserted within the concave surface of agasket of the invention two effective seal barriers are formed oninitial compression thus providing double the sealing integrity of aconventional single line seal such as that obtainable with an O-ring.The relatively enlarged edges of the new gaskets, as described above,also provide wedge-shaped sealing segments which prevent the gasketsfrom being extruded through the opening to be sealed between two flangesand in fact provide for an ever tighter seal as the pressure on the edgeof the gasket is increased. This effect is clearly illustrated in FIG. 5wherein the arrows indicate pressure forcing the enlarged left edge ofthe gasket into the space to be sealed. While FIG. 5 shows the initialrelationship between the gasket and flanges for purposes of clarity, itwill be appreciated that in the final sealed condition the flanges 28would be drawn together so as to contact the gasket surfaces throughmost or all of the width of the flanges. It will also be appreciatedthat the thickness of the latex coating surrounding the dimensionallystable inserts in the new gaskets varies on the several surfaces andedges as necessary or desirable depending upon the use and in useenvironment of the gasket. More specifically, relatively thick coatingsare normally desirable on the upper and lower surfaces and inner edge ofthe gaskets to provide the desired sealing integrity, but a relativelythin coating may be employed on the outer edge of the gasket, sincethere is no risk of fluid strike through at that edge.

While the present invention has been described in conjunction withcertain preferred embodiments thereof and certain methods of makingthese embodiments, it is to be understood that this has been done bywayof illustration only and is not to be construed as limiting theinvention, the scope of which is delineated only by the prior art andthe annexed claims.

What is claimed is:

1. an automotive valve cover gasket comprising a flexible substantiallyincompressible planar fibrous inner member enveloped in an externalcoating of a Thickness in Inches Approximate Range Maximum MinimumFinished Gasket 0.250 0.063 lnner Member 0.094 0.031 Rubber Coatings:

Upper Surface 0.094 0.016 Lower Surface 0.094 0.016 lnner Edge 0.0940.016 Outer Edge 0.094 0.016

3. An automotive valve cover gasket according to claim 2 wherein thefinished gasket has a thickness of about 0.156 inch, an inner memberabout 0.062 inch in thickness, upper and lower surface coatings about0.047 inch in thickness and edge coatings of about 0.016 to 0.094 inchin thickness.

2. An automotive valve cover gasket according to claim 1 having thefollowing dimensions: Thickness in Inches Approximate Range MaximumMinimum Finished Gasket 0.250 0.063 Inner Member 0.094 0.031 RubberCoatings: Upper Surface 0.094 0.016 Lower Surface 0.094 0.016 Inner Edge0.094 0.016 Outer Edge 0.094 0.016
 3. An automotive valve cover gasketaccording to claim 2 wherein the finished gasket has a thickness ofabout 0.156 inch, an inner member about 0.062 inch in thickness, upperand lower surface coatings about 0.047 inch in thickness and edgecoatings of about 0.016 to 0.094 inch in thickness.